1. Field of the Invention
This invention relates generally to automatic test equipment for electronics, and, more particularly, to the control of instrumentation of automatic test equipment for interacting with devices under test.
2. Description of Related Art
Automatic test equipment, or “ATE,” is an integral part of electronics test and manufacturing. What began decades ago as collections of manually operated benchtop instruments has evolved into highly integrated systems optimized for precision, speed, and control.
FIG. 1 shows an simplified example of a modern ATE system, or “tester.” The tester includes a host computer 110 that controls electronic subsystems 112-118. The electronic subsystems are wired to an interconnect 120, which selectively connects signals from the subsystems to a unit under test, or “UUT” 122, under control of the host computer 110. The UUT is generally a manufactured device or assembly, or a partially manufactured device or assembly, on which electronic testing may be conducted.
The electronic subsystems may include, for example, a power subsystem 112, a digital subsystem 114, an analog subsystem 116, and a microwave subsystem 118. Each subsystem includes instruments. For example, the power subsystem 112 may include fixed power supplies (112a and 112b) as well as various user-programmable power supplies (112c-112d). The digital subsystem 114 may include digital drive/detect instruments (114a-114b) for sourcing digital signals to the UUT 122 and detecting the levels of digital signals produced by the UUT. It may also include a timing generator 114c and a pattern generator 114d. The analog subsystem 116 may include a parametric measurement unit (PMU) 116a, digitizer 116b, arbitrary waveform generator 116c, and timer/counter 116d. The microwave subsystem may include a continuous wave (CW) microwave synthesizer 118a, modulated wave synthesizer 118b, and multi-tone synthesizer 118c, as well as a microwave receiver 118d. 
The interconnect 120 is generally an array of switches and connectors arranged for flexibly connecting the instruments of the subsystems 112-118 to different electronic nodes, or “pins,” of the UUT 122.
The host computer is the control center of the system. It is configured with computer software for creating and executing “test programs,” i.e., collections of user or machine-generated code for testing a UUT. The computer software includes a programming language as well as numerous instrument drivers. The programming language is sometimes a standard computer language, such as Microsoft Visual Basic™. Alternatively, the programming language may be proprietary to the ATE manufacturer, or a combination of standard and proprietary components. The instrument drivers are generally proprietary to the instrument manufacturers.
The role of an instrument driver is to control an instrument. It can generally write to the instrument to configure and activate it and read from the instrument, for example, to determine measured results. The driver exposes one or more software functions to the test program. The test program generally accesses the driver via function or method calls inserted into the test program.
An example of a tester programming language is VBT™, or “Visual Basic for Test,” which is used in the Flex™ line of testers produced by Teradyne, Inc. of North Reading Mass. VBT is a modified form of VBA™ (Visual Basic for Applications), and is accessed through a customized version of Microsoft Excel™, known as IG-XL™. Instrument drivers for IG-XL are provided as software modules accessible by a VBT test program.
A longstanding organizing principle of ATE system architecture is to provide a three-way correspondence between instrument function, instrument assembly, and instrument driver. An instrument for performing any given function is generally housed in a physical assembly unique to that instrument and is controlled by a driver unique to that instrument. Different instrument functions are provided in different physical assemblies and are controlled by different drivers.
FIG. 2 illustrates this correspondence. A test program 210 includes function calls to instrument drivers 212, 214, and 216. Each of these drivers controls a single instrument function. Instrument functions are provided in distinct instrument assemblies 222, 224, and 226.
The three-way correspondence offers many benefits. It is simple to use. To control an instrument, a user simply makes one or more function calls to the instrument's driver. The driver's functions are generally a direct reflection of the instrument's capabilities. The three-way correspondence also avoids many hardware conflicts. Because each instrument is a separate assembly containing essentially all the hardware needed to achieve its functionality, the instrument can be configured over the full range of its functionality without concern about how other instruments in the system are configured or whether resources needed for certain functions are available.
We have recognized that this organizing principle may not be optimal, however, particularly going forward. ATE manufacturers are engaged in continuing efforts to reduce costs, power, maintenance requirements, and the physical space occupied by instruments. An effective way of supporting these efforts is through integration of instrument hardware, where different instrument functions are combined on single, or smaller numbers of, assemblies.
We have recognized, however, that instrument integration presents design challenges. These challenges essentially involve maintaining much of the simplicity of use and avoidance of hardware conflicts that the three-way correspondence provided. What is needed is an integrated instrument architecture that addresses these challenges.